1. Field of the Invention
The present invention is directed to an inspiratory tube intended for use as at least a part of an overall inspiratory line in a ventilator, the inspiratory tube being of the type having a tube wall, distal and proximal ends, a gas flow channel for carrying a flow of breathing gas, and an opening in the wall at a distance from the distal end of the tube, the opening being adapted for connection of an expiratory device thereto.
2. Description of the Prior Art
An inspiratory tube of the above type is described in PCT Application WO 94/06499. This known ventilator has an inspiratory tube connected to a gas source at one end and to the patient at the other end. An expiratory valve is connected to the inspiratory tube at a specific distance from the patient. In one embodiment, the expiratory valve is connected to a second gas source for the purpose of maintaining a pre-adjustable Positive End-Expiratory Pressure (PEEP). In another embodiment, the expiratory valve is instead connected to the gas source via a valve system in order to maintain PEEP. A pressure gauge and flow meter are arranged in the inspiratory tube between the gas source and the expiratory valve. A control unit controls the entice ventilator. This known ventilator is primarily intended for use as a home care ventilator, i.e. a respirator a patient can use at home.
Interest in home care ventilators is steadily increasing. This is because such a device is advantageous to the patient, who is able to be in her/his own home and can enjoy a greater degree of mobility. There are also public health benefits, since home care frees hospital resources by reducing in-patient treatment time, beds in intensive care being particularly costly. This type of ventilator can be battery-powered and is sometimes referred to as a `portable` ventilator. Despite this terminology, such a ventilator usually weighs quite a few kilograms and can only be carried around with some difficulty, even by healthy people.
A genuinely portable ventilator, i.e. a ventilator (weighing up to 1 kg, preferably less than 500 g) the patient is easily able to carry, with a capacity sufficient to provide respiratory assistance for several hours, would be even more desirable for patients. Miniaturizing a ventilator to this extent, employing modern turbine, battery and microprocessor technology etc., is thoroughly feasible. One important factor in this process would be to retain every essential function available in a conventional ventilator, such as the ability to maintain a PEEP, to as large an extent as possible. Such a fully portable ventilator would be suitable for virtually every kind of patient. It even could be used as an emergency ventilator for a number of applications and could be included in the basic equipment of e.g. aircraft, buses, boats, ambulances, fire engines, etc.
The known inspiratory tube described above has limitations, since a number of connectors are needed for the pressure gauge and flow meter. This known inspiratory tube also has a design that limits its usefulness and makes the use of separate gas sources or special valve systems necessary for controlling the expiratory valve etc. connected to the inspiratory line.